In a conventional inkjet recording mode, in response to electric signals from computers or the like, ink droplets are jetted at fast speed from a print head or spray nozzle onto the material to be recorded, applying prints onto the ink-receiving layer of that material. This inkjet recording mode, because of running quiet and being capable of fast printing, is gaining popularity for use on copiers, facsimiles, posters, displays or the like. Inks used in the inkjet recording mode must suffer from no change with time, maintain the sufficient density of images stably over an extended period of time, and allow images printed onto the material to be recorded to excel more in the ability to reproduce the original.
In general, inks have been prepared by blending coloring materials such as dyes or pigments, a dispersant for dispersing them and a solvent, optionally with additives. However, oil inkjet printers are often used out of doors, and so weight is given to the robustness of the coloring materials.
Applicant has already filed a patent application (Patent Publication 1) for an oil ink composition for inkjet recording purposes, which is well fit for printing onto polyvinyl chloride base materials and improved in terms of all the quality of prints, stability upon printing, the ability of prints to be dried, and ink storage ability. This oil ink composition uses as solvents polyoxyethylene glycol dialkyl ether solvents and/or cyclic ester solvents, and is now used even indoors because of being of great safety. On the other hand, aqueous inkjet printers are mainly used indoors, and so weight is given to color saturation rather than robustness, as shown typically in Patent Publication 2. Oil ink compositions going into indoor applications, too, must have color reproduction capabilities and color saturation on a par with those of aqueous inks and produce images having high color reproduction capabilities and color saturation. For oil inks, there is mounting demand for improvements in color reproduction capabilities on recording media.
Patent Publication 1: WO 04/007626 Pamphlet
Patent Publication 2: JP(A) 2007-297595